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WATCH: NDP Ethics critic MP Charlie Angus says they want to know why Nigel Wright and other PMO staffers were not charged by the RCMP for involvement in the Mike Duffy senate expense scandal.

OTTAWA – The NDP has asked Canada’s director of public prosecutions to look at the evidence collected by the RCMP in the Mike Duffy case to determine if charges should be laid against other people as well.

“I have written to the director of public prosecutions requesting that he review the evidence collected by the RCMP and make his own determination as to whether Nigel Wright and/or any of the prime minister’s staff involved in the Wright-Duffy scandal should be charged under the Parliament of Canada Act,” Angus said.

“Such a case, given its political sensitivities, is precisely the reason the director of public prosecutions was established.”

Angus said he doesn’t question the RCMP investigation, but insisted the independent director of prosecutions should have been involved. A review of the evidence might settle some questions that have swirled around the Duffy scandal, he added.

However, Dan Brien, a spokesman for the Public Prosecution Service of Canada, said Tuesday that Angus’s request for a review of the evidence is misplaced.

Some parliamentary law experts, such as former House of Commons law clerk Rob Walsh, speculated that the RCMP may have been reluctant to pursue charges under the Parliament of Canada Act because there is no record of anyone ever before being prosecuted under sect. 16.

That section stipulates that it’s an indictable offence – punishable by a year imprisonment and a fine of $500 to $2,000 – to offer compensation to a sitting senator in regard to “any claim, controversy, arrest or other matter before the Senate.”

The Public Prosecution Service of Canada would have been responsible for prosecuting any charges laid under the Parliament of Canada Act. Yet the RCMP never consulted the service before declaring in April that the evidence did not support laying charges against Wright.

Walsh and other parliamentary law experts have argued the Parliament of Canada Act would have been an easier route to secure a conviction against Wright because, unlike Criminal Code offences, no proof of intent to act corruptly is required.

Wright has long insisted that he did nothing wrong and that his only motivation was to ensure taxpayers were not left on the hook for Duffy’s disputed expense claims.